1. Field of the Invention
The present invention relates to a mobile communication system, a location manager and a routing manager, and in particular to a method for managing location and performing paging in a mobile communication system.
2. Description of the Related Art
As is well known, it is common in mobile communication services to store the location of each mobile node, such as a cellular telephone, in a location manager in order that the mobile node can receive termination (incoming call/packet) wherever it is. Specifically, an area, for which a mobile communication service is provided, is divided in multiple registration areas, and when a mobile node moves from one registration area to another registration area, a location update request, in which a registration area after movement is identified, is sent from the moving node to the mobile network via an base-station apparatus, consuming wireless resources. In response to the location update request, the registration area of each mobile node, which is stored in the location manager is sequentially updated.
However, when a lot of mobile nodes simultaneously move in a moving body, for example, when there are a lot of passengers carrying a mobile node in a train, a lot of mobile nodes move at the same time as the train moves, and if the train moves from one registration area to another registration area, a location update request is sent to a mobile network from each of these mobile nodes via an base-station apparatus. This causes problems such as pressure on wireless resources and temporary, significant increase in communication traffic in the mobile network.
Techniques for solving these problems are disclosed in Patent Document 1 and Non-patent Document 1, for example. In these documents, a mobile communication system is disclosed in which a master-slave relationship is established between a moving body, such as a train, and a mobile node existing in the space in the moving body so that a mobile router installed in the moving body, which is a master, sends a location update request of the mobile nodes, which are slaves, to the mobile network on behalf of the mobile nodes, consuming wireless resources. In this mobile communication system, a mobile node existing in the space in a moving body registers its location with the above mobile router as a virtual base-station apparatus. When the moving body moves from one registration area to another registration area, the mobile router sends a location update request to the mobile network via a base-station apparatus. In this way, it is realized that the mobile router sends a location update request of mobile nodes existing in the space in a moving body.
(Patent Document 1)
Published Unexamined Patent Application No. 11-355835
(Non-Patent Document 1)
“A Study on Concatenated Mobility Management” by Yumiba, Sasada, Fujiwara and Yabusaki, IEICE Technical Report; N2000-177, pp. 7-14; February 2001
However, the mobile communication system disclosed in the above published unexamined patent applications and the like has the following problem. That is, when all the mobile nodes (hereinafter referred to as MN for short) existing in the space in a moving body and a mobile router (hereinafter referred to as MR for short) installed in the moving body and performing location update (hereinafter referred to as LU for short) move together in a dormant state, it is necessary for the MR, each time they move from one location area (hereinafter referred to as LA for short) to another location area, to send an LU signal to a location manager (hereinafter referred to LM for short), which retains location area information for the MNs and the MR, in order to update information for the LA where the MR exists.
However, if the MR itself is in communication, or one or more MNs, which are in a master-slave relationship with the MR, is in communication via the MR, for example, the MR, which is not dormant, does not send an LU signal even if they move to different LAs. Therefore, the LA of the MR cannot be updated in the LM. This causes a problem that the MN cannot receive the paging.
The present invention has been made in consideration of the above problem, and its object is to provide a mobile communication system, a location manager and a routing manager capable of minimizing use of finite wireless resources and enabling paging to be performed to an MN even when an LM does not necessarily retain correct LA information, for example, for the reason that the MR, performing LU of MNs existing in the space in a moving body on behalf of the MNs, does not send an LU signal because it is active.